N49746

HISTORY OF FLIGHTOn October 2, 2014, about 1255 central daylight time, a Bell 206B helicopter, N49746, had a hard landing following a loss of tail rotor effectiveness near Woodsboro, Texas. The airline transport rated pilot and two passengers received serious injuries. The helicopter sustained substantial damage during a subsequent roll over. The helicopter was registered to and operated by an individual doing business as Heartland Helicopters under the provisions of Code of Federal Regulations Part 91 as an aerial observation flight. Day visual flight rules conditions prevailed for the flight, which did not operate on a flight plan. The flight originated from the Alfred C 'Bubba' Thomas Airport (T69), near Sinton, Texas, about 1200, and was destined for the Beeville Municipal Airport, near Beeville, Texas.

According to the pilot's accident report, the purpose of the flight was a laser examination of a pipeline to detect methane gas. He indicated that he was flying the helicopter between 35 and 40 meters above ground level. The pilot reported that the helicopter suddenly yawed to the right without warning. He indicated that he did not recall "when a warning horn went off, but there was a warning horn." He recalled it as a low rotor rpm warning. The pilot stated that there were wires to his right side and building structures on his left. The pilot reported the helicopter yawed, he indicated he was sure he applied pressure to the left pedal, and a loss of tail rotor effectiveness occurred. The pilot said that the helicopter hesitated turning right for a "short" period of time and then continued the turn to the right. He intended to guide the helicopter away from the wires and structure. However, the helicopter continued one full revolution to the right. The pilot, in part, stated:

It was at this point I had two thoughts. I need to reduce collective in order to maintain sufficient rotor speed to cushion the landing. I also did not roll off the throttle because I did not want to shut down a good engine if I had one. I did my best to land the aircraft in a level and stable manner. The aircraft impacted the ground. I do not remember bouncing, but we impacted and rolled to the right and ended up with the aircraft positioned on the right side.

According to a passenger on the pipeline inspection flight, he heard another passenger guide the pilot to make a right turn as the helicopter approached a set of power lines. He felt the helicopter change "position" while making the turn. The passenger then "heard a change, decrease, in the engine RPM, followed almost immediately by a warning horn" and he "heard the pilot say that he had a low tail rotor warning." The helicopter started to spin and the he braced for impact. When asked to describe the sounds he heard, the passenger reported that the engine sounded "similar to that of a lawnmower, running at a normal speed and how it bogs down in tall weeds or grass. The engine bogging was immediately followed by the master warning horn." PERSONNEL INFORMATIONThe pilot, age 47, held a Federal Aviation Administration (FAA) airline transport pilot certificate with an airplane multi-engine land rating. He held commercial pilot airplane single-engine land, rotorcraft helicopter, and instrument helicopter privileges. He held a flight instructor certificate with airplane single-engine and rotorcraft helicopter ratings. He also held a flight engineer certificate with a turbojet powered airplane rating. He reported that he held a FAA second-class medical certificate dated August 15, 2014, with a limitation that he must wear corrective lenses. His most recent flight review was completed on May 20, 2014. The pilot's report indicated that he accumulated a total flight time of 13,916 hours, of which 2,376 hours were in rotorcraft and 35 hours were in the same make and model as the accident helicopter. AIRCRAFT INFORMATIONN49746 was a 1976 model Bell 206B helicopter with serial number 1928. A 420-shaft horsepower Rolls Royce 250-C20B engine with serial number CAE-834605 powered the helicopter. It was a five-place, single main rotor helicopter with a tail mounted anti-torque rotor. According to the pilot's accident report, the helicopter was maintained under a manufacturer's inspection program and its last inspection was a 100-hour inspection dated June 5, 2014. The helicopter accumulated 18,323.2 hours of total flight time at the time of the inspection. According to National Transportation Safety Board (NTSB) report FTW81DRA33, the helicopter was involved in a prior accident on May 19, 1981, when it sustained substantial damage during a takeoff accident in the Gulf of Mexico.

The helicopter was fitted with a Pergam Aerial Laser Methane Assessment (ALMA) device. The Pergam website indicated the system is a laser based natural gas detection system. ALMA consists of an on-board laptop that manages the data acquisition and data processing, an on-board electronic laser-control system, a GPS receiver, and a helicopter belly-mounted optical unit. The optical unit is a refraction-based system, which consists of a laser, a reference channel, and three digital video recording cameras. The cameras are integrated into the ALMA system and indicate the location that is scanned by the system's laser beam. According to the website, it is simultaneously used to help the pilot position the helicopter over the object that needs inspection.

A copy of a fuel receipt indicated the helicopter was serviced on October 2, 2014, with 60.1 gallons of Jet A fuel at T69. METEOROLOGICAL INFORMATIONAt 1353, the recorded weather about 17 miles and 122 degrees from the accident site at the Aransas County Airport, near Rockport, Texas, was: Wind 170 degrees at 10 knots, gusting to 21 knots with winds varying from 130 degrees to 190 degrees; visibility 10 statute miles; sky condition few clouds at 1,600 feet, scattered clouds at 2,400 feet, broken clouds at 2,900 feet; temperature 32 degrees C; dew point 26 degrees C; altimeter 29.86 inches of mercury. The field elevation at the airport was about 24 feet above mean sea level (MSL). AIRPORT INFORMATIONN49746 was a 1976 model Bell 206B helicopter with serial number 1928. A 420-shaft horsepower Rolls Royce 250-C20B engine with serial number CAE-834605 powered the helicopter. It was a five-place, single main rotor helicopter with a tail mounted anti-torque rotor. According to the pilot's accident report, the helicopter was maintained under a manufacturer's inspection program and its last inspection was a 100-hour inspection dated June 5, 2014. The helicopter accumulated 18,323.2 hours of total flight time at the time of the inspection. According to National Transportation Safety Board (NTSB) report FTW81DRA33, the helicopter was involved in a prior accident on May 19, 1981, when it sustained substantial damage during a takeoff accident in the Gulf of Mexico.

The helicopter was fitted with a Pergam Aerial Laser Methane Assessment (ALMA) device. The Pergam website indicated the system is a laser based natural gas detection system. ALMA consists of an on-board laptop that manages the data acquisition and data processing, an on-board electronic laser-control system, a GPS receiver, and a helicopter belly-mounted optical unit. The optical unit is a refraction-based system, which consists of a laser, a reference channel, and three digital video recording cameras. The cameras are integrated into the ALMA system and indicate the location that is scanned by the system's laser beam. According to the website, it is simultaneously used to help the pilot position the helicopter over the object that needs inspection.

A copy of a fuel receipt indicated the helicopter was serviced on October 2, 2014, with 60.1 gallons of Jet A fuel at T69. WRECKAGE AND IMPACT INFORMATIONThe helicopter impacted a field near Woodsboro, Texas, and was relocated to a local salvage yard. The NTSB investigator in charge (IIC) examined the wreckage at the salvage yard with the engine manufacturer. The observed damage and deformation was consistent with the pilot's report of the helicopter coming to rest on its right side. The helicopter's mast exhibited a separation, which was consistent with overload. The main rotor blades exhibited damage consistent with impact with terrain. The helicopter's transmission rotated when manipulated by hand. The tailboom was separated from the helicopter fuselage and the tail rotor driveshaft inside exhibited a separation consistent with being cut by recovery personnel. The tailboom separation exhibited deformation consistent with its contact with terrain during a helicopter rollover to the right. The tail rotor blades were intact on the aft portion of the tailboom. The skids exhibited deformation and separations consistent with overload. There was a tear observed in the lower portion of the fuel cell. Both of the cell's fuel boost pumps were intact and they pumped fuel when electrical power was applied to them. Airframe filters were opened and no anomalies were observed within them. The tail rotor and main rotor systems moved when the turbine blades inside the exhaust were rotated by hand. No airframe pre-impact anomalies were observed. The engine did not exhibit any exterior damages and it was separated from the airframe for a teardown examination.

The engine was examined under supervision of the IIC at the engine manufacturer. Disassembly did not reveal any anomalies that would have precluded engine operation. The engine's fuel control and governor were hand carried by the IIC for testing at their manufacturer. ADDITIONAL INFORMATIONFAA Advisory Circular 90-95 - Unanticipated Right Yaw in Helicopters and the Helicopter Flying Handbook describe the phenomenon of loss of tail rotor effectiveness (LTE). The handbook, in part, stated:

LTE or an unanticipated yaw is defined as an uncommanded, rapid yaw

towards the advancing blade which does not subside of its own accord.

It can resu...